Telegraph receiving system



June 19, 1934. w. G. PLUM-m 1.963.618

TELEGRAPH RECEIVING srs'rzu am June 11. 1931 A INVENTOR \lmlr W W. G.FLUHARTY -v BYM ATTORNEY 6 6 "row-a graph line or cable.v

5 slowly and ordinarily does not reach. its full am- Patented June 19,1934 1 *UNITEDS A PATENT FIC 1 j TELEGRAPH RECEIVING SYSTEM. 7

William G; Fluharty, Rockville Center, N. Y., as-

. signor to 'The- Western Union Telegraph Coinpany, New York, N. Y., acorporation of New,

. York Application June 11.61931, sw rm. 543,712

' V .11 claims- (o1. 118588) ,g'Ifhis invention relates to a method andapparatus for receiving telegraphv signals, and more particularly to thecounteracting of the distorting eflects of capacity and induction in along tele- Long telegraph conductors and cables have a considerableamount of distributed capacity and V induction which materially distortthe arrival means for counteracting; the signal distortion willhereinafter appear.

currents so that, in many cases the regular telegraph relays, eithersingle current'orfpolarized,

will not accurately respond to at economical frequencies.

signals transmitted 'The arrival curve of-a signahover a line conductorhaving considerablecapacity builds up plitude or'steadystate before thesucceeding re-. versal occurs. However, if along signal isreceivedjfollowed by a short reversal the long signal i may attain suchamplitude at the time the reversal occursthat the subsequent reversalwill not reduce the line current to zero. In such cases there would beno reversalof current through the coilSLof thefpolarized receiving relayto actuate itsarmature and'the impulse would be lost. 7

,i ',Various arrangements have been devised, in ocean cable workforovercoming these defects or difliculties, such the a usual vibrating.circuits or signal interpolating schemes but such apparatus is of adelicate, sensitive character and its use is precluded from overlandwork due. to the initial, cost of installation and. the cost ofmaintenance and operation thereof. 1 1 7 'It isone of theobjects of thepresent invention, therefore, to produce a simple and inexpensivefactors'present in transmission'line conductors havingi'a large'amountof distributed capacity;

l Anothe'r object is to enable the speed of transmission overisuchlinesto bematerially increased.

f Ajfurther ,object 'isto compensatefor the 'e1.'-. fects of, theindividual signals on the receiving.

relay due to "difierence in the lengthor duration thereof.

A'still'further object is to create an artificial zero line forreceived'signals such that all signals will have approximately equal,amplitudes with respect thereto regardless of, the length or duration oftheflsignal. j

other obJe'ctS and adva tages" e nvepy a-polarized'relay in the linecircu t would not respond to the reversal B and this signal would be Laccordance with my invention I employ a polarizedfreceiving relay havinga biasing coil which produces'a' flux 'neutralizinga portion ofthe-'flux'produced bythesignal current flowing throughth main-linewinding Of the relay. The

for a portion of the: signal current.

biasing 'coil preferably is provided .with" current from a local sourceunder the control or theirelay tongue and has a time constant simulatingthat of the arrivalcurrent so that the instantaneous value of thecurrent in the biasing coil bearsa fixed ratio to. the instantaneousvalue of the line current; The time constant of the biasing coil isproduced byflvariable ind'uctanc'ein series there-, with which controlsthe rate of increase of. flux in the coiland a Variable resistance alsoin series therewith for controlling the maximum am plitude oftheopposing current. I

a The biasing coil in effect shifts the zero .line relativetothe'signals so that itbears a fixea relation to the amplitude of eachreceived. sign'alfi' I The invention will be more 'fully understood byreference to the accompanying .drawing, inwhich: In Fig. 1 shows theapproximate shape of thejar rival curves of signals overa telegraphcable or lineof considerablelength; I V i I 'Fig." 2 shows the samecurve with the absolute zerofline replaced by" a resultant zero obtainedwith the arrangement oi the present invention. 'Fig. 3 is afcircuitdiagram'of a receiving system embodyingthe invention; f 7 I Fig.4 is acircuit'diagram of a modified receiv-f ing' system employing theinvention. Fig. 5 is'a modified arrangement in which the current for thecompensating winding is taken from the line, a'nd Fig. ,6 isa furthermodification in which compensation is effected by a leakage path toground,

. The principal factors which produce losses upon the arrival currentsover long telegraph lines or cables are resistance self-inductionandcapacity, capacity ordinarily exerting the great;

es't'distorting effect. Figure 1 shows the approximate shape bf typicalarrival curves over the line: conductors containing'a' large amount ofcapacity;

The first'signal A which re re ents a long. spacf 10st. The markingsignalD dips slightlybelow the zero line and may for may not operate therelay depending onthe sensitivity thereof and at bestwould only cause amomentary operation thereof registering what is termed a pin dot.Similarly a long marking signal such as F builds up in amplitude to suchan extent that the succeeding spacing signal G may not reach the zeroline so as to be recorded. When uniform alternations of the signal occursuch as indicated at J, K, L, M, and N, they may be positionedsubstantially symmetrical of the zero line and will properly actuate theline relay, if it is sufficiently sensitive.

Figure 2 shows the same arrival curve with the absolute zero replacedwith a resultant zero ra:' which approximately intersects the centralportion of each wave. It will be noted that all of the signals are ofsubstantially equal amplitude with respect to this artificial zero. Ihave found that if the receiving line relay be biased in such mannerthat the opposing flux produced in the biasing winding bears the samerelation to the flux produced by the main line winding as the resultantzero a:':s bears to the signal wave, that all signals will be properlyrecorded and with signal frequencies far in excess of those ordinarilyobtainable with the usual type of receiving relays.

Referring now to Figure 3 the incoming line ML which may be ofconsiderable length, having a large amount of capacity, is terminated inthe main line winding 11 of the'receiving relay RR and the ground 12. Abiasing winding 13 is provided for the relay, having one terminalconnected to the tongue T of the relay, whereby battery of eitherpolarity may be applied thereto, and the opposite terminal connectedthrough a variable inductance 1(1 and a variable resistance 15 to theground. The local relay LR may be operated from the tongue of thereceiving relay and a spark quenching arrangement including theresistance 16 and a condenser 17 may be provided.

The operation of the receiving relay is as'follows. Assume that therelay tongue is on its left hand contact when the signal A is received.Positive current will then flow from the spacing contacts through thetongue of the relay and thence to the biasing coil and the adjustedinductance and resistance to ground. The current through the biasingcoil is of such duration that it tends to oppose the flux in the mainline coil 11, due to the received line current but its rate of riseiscontrolled by the adjusted inductance in series therewith so thatitapproximates the rise of flux in the main line coil due to the receivedsignal A. The current through the biasing winding may be represented bythe line g y in Figure 2. ing the opposing flux in the winding 13 fromthat generated by the line current the resultant effective value thereofis represented by the shaded portion of the signals, shown in Figure 2.At the termination of the signal A when the current crosses theresultant zero ar'a: at the point 20, the tongue of the relay will moveover against its marking contact and the reversal B will besatisfactorily recorded, even though the line current does not cross theactual Zero line. While the relay tongue is resting against its markingcontact current begins to flow in the reverse direction through biasingcoil but the series inductance prevents a sudden rise of current, thusenabling the next signal to be properly received. If the values of theinductance and the resistance are properly adjusted the flux on thebiasing coil will increase and decrease in definite relation to thereceived signals and will in eifect shift the zero line a::z: so that itundulates with the re- Subtract-' ceived signals, so that each reversalis of substan tially equal amplitude with respect thereto.

The inductance 14 may be of the usual laminated core type but preferablyI employ an inductance arrangement consisting of a combination of aninductance element having a solid iron core and an inductance elementhaving a laminated iron core. By properly adjusting the values of suchinductances the time constant of the biasing winding can be made toapproximate very closely the shape of the arrival curve. In Figure 4, Ihave shown the biasing winding 13 applied to a vibrating relay VR. Thisrelay in addition to the line winding 11 and biasing winding 13 isprovided with an opposing winding 21 and an accelerating winding 22. Theopposing winding is connected between the relay tongue and the groundthrough a variable resistance 23 and the accelerating winding 22 isconnected between the relay tongue and the ground through a variablecondenser 24.

In the operation of the relay, the biasing winding 13 opposes the linewinding was to compen sate for the retardation of linesignals. With therelay tongue on its left hand contact, current will be supplied to theopposing winding 21 from the relay contact through the'resistance 23 andis in such direction as to oppose the current flowing through the linewinding 11 thus tending to move the armature towards its right hand ormarking contact. As the resultant'fiux produced by current flowing inthe line winding 11 and the biasing winding 13 falls to a value slightlyless thanthe magnetic effect of the opposing current in the coil 21, thearmature starts to move away from the spacing contact. When the armatureleaves the spacing contact, the accelerating condenser 24 dischargesthrough the accelerating winding 22 thereby causing the current to flowtherein in such direction that it acts upon the armature to carry itquickly across to the marking contact. The current in the opposingwinding 21 falls to zero duringthe time in which the armature travelsfrom one contact to the other. When the armature strikes the spacingcontact, the accelerating condenser again charges up in such directionas to hold the'armature firmly on its contact so as to prevent ,reboundthereof.

The biasing coil 13 and the coil 21 both oppose In Figure 5 the currentfor the compensating winding 13 is taken directly from the line inoppositionof the main winding 11 by a leakage path to ground through theinductance 14 and resistance 15. The scheme has the advantage that thebuild-up of current in the compensating winding responds more quickly tothe reversals of signals, since it does not have to await the operationof the relay tongue. A variable resistance 25 is inserted in series withthe windingll to enable the current to divide properly between thewindings 11 and 13.

While this circuit produces better shaping of the signals, than thearrangements ofFigures 3 and 4, it causes a reduction in the currentthrough the main line winding and therefore, in certain instances maynot be as suitable for high frequency signaling on lines of highattenuation. Figure 6 shows a compensating circuit in whichv the linecurrent is varied at the receiving terminal, to cause the signals toassume a symmetrical form relativertothe zero line. A portion of thesignal current is leaked. off through the variable inductance 14 andvariable resistance 15. The inductance 14 is of a type which will notvary appreciably within the range of signalling current. The inductanceof the relay winding 11 due to the lack of sufiicient iron, eddy currentlosses etc., is of a less efficient nature, whereby the higher frequencysignals, such as the short reversals B, C, D and E are very nearlyblocked by the inductance 14, flowing mainly through the relay winding11 and the lower frequency or long Therefore, I do not desire to belimited to the exact circuit arrangement shown but include allmodifications and adaptations that come within the terms of the appendedclaims.

What I claim is:

1. In a telegraph system, a line 'over which current variations arereceived, a relay having a main line winding in said line, an opposingwinding for said relay, a variable inductance and a variable resistancein circuit with the opposing winding and means dependent upon saidcurrent variations for energizing said opposing winding through saidinductance and'resistance, said inductance and resistance beingproportioned so as to cause-the current to build up in the opposingwinding in definite relation to the rate at which 7 the'current buildsup in the main line winding.

2. In a telegraph system, a line over which current variations arereceived, a relay having a main line winding in said line, an opposingwinding for said relay, an inductance in circuit with the opposingwinding and means dependent upon said current variations for energizingsaid opposing winding through said inductance, said in ductance beingproportioned so as to cause the rate of increase of current thereintobear a defi-' nite relation to the rate of increase of current in themain line winding.

3. In a telegraph system; a line having an appreciable amount ofdistributed capacity, and a relay in said line having a main winding andan opposing winding, said opposing winding being controlled by thearmature of the relay and having a time constant which simulates thetime v constant of the line.

4. In a telegraph system, a line having an appreciable amount ofdistributed capacity, a relay in said line having a main winding and anopposing winding, said opposing winding being controlled by the armatureof the'relay and having inductance and resistance in series therewithof'such value that the time constant of the opposing winding simulatesthe time constant of the line.

5.'In a. telegraph system, which includes a transmission line having anappreciable amount of distributed capacity and inductance wherebysignals transmitted over said line arematerially retarded, a relay intheline, and means for variably biasing saidrelay in opposition to saidsignals in proportion to the amplitude of individual received signalimpulses in such manner thatall impulses have a substantiallyuniformefiect 'on' the relay armature.

6. In a telegraph system, arelay having a main line winding, anaccelerating winding and an opposing winding, said opposing andaccelerating winding being controlled from the contacts of the relay andsaid opposing winding being in cluded in 'a circuit having a timeconstant ap-.

proximating that of the line.

7. In a telegraph system, a relay having a main line winding and anopposing winding, means in circuit with the opposing winding for causingthe flux therein to vary in proportion to the variations. in flux in themain line winding, and means for limiting the current in said opposingwinding to a predetermined value. V

8. The method of recording telegraph signals received over aline havingappreciable distorting efiects on the arrived signals whereby said sig--nals vary in amplitude comprising, producing anartificial zero linewhich fluctuates in accordance with variations in amplitude ofindividual signal impulses and recording the signals with respect tosaid artificial zeroline.

9. The method of recording telegraph signals received over a line havingappreciable distorting effects on the arrived signals whereby saidsignals vary in amplitude, which comprises producing a flux inproportion to the received signal current, producing an opposing flux oflesser magnitude which varies in definite relation to the receivedsignal currents, and utilizing the resultlngflux to actuate a recordingdevice.

10. In a telegraph system a line, a relay having a main winding and anopposing winding, both re ceiving current from said line, and means incir- I cuit'with said opposing winding for causing current to build uptherein in proportion to but at a lower rate than in said main linewinding.

11. In a telegraph syst'em,a line having an appreciable amount ofdistributed capacity and .inductance whereby signals transmitted .oversaid -line are materially retarded, a receiving instrument'having a mainwinding in said line, and a shunt path around said main windingcontaining fan inductance of a value to bypass a greater proportion oflow frequency signals, than of thehigh .frequency signals, said shuntpath including a winding arranged to produce a flux opposing that in themain winding.

WILLIAM G; FLUHAR'I'Y.

